Short- and long-term effects of crop residues and of phosphorus fertilization on pearl millet yield on an acid sandy soil in Niger, West Africa

Abstract

Abstract Field experiments were conducted during the rainy seasons of 1990 and 1991 on an acid sandy soil (Luvic Arenosol) in Niger, to assess long-term (since 1986) and short-term (since 1990) effects of millet straw (crop residues) at different amounts (2 t and 6 t ha−1) and modes of application (incorporation, mulching and burning), and of phosphorus (P) fertilization on dry matter yield of pearl millet [Pennisetum glaucum (L.) R. Br.]. Especially long-term, but also short-term application of crop residues increased dry matter yield of pearl millet by more than 60%, whereas their omission decreased yield immediately. Compared to mulching or burning, higher yields were obtained with incorporation of crop residues. When crop residues were applied as mulch, dry matter yield was increased to the same extent by 2 t and 6 t ha−1. Similar dry matter yields were achieved with crop residues (-P) to those with P fertilizer only. An additional yield increase could be obtained by simultaneous application of crop residues and P. Without crop residues, potassium (K) concentrations in the shoot dry matter indicated K deficiency. With crop residues considerable amounts of K (15 kg t−1) were provided and raised the K concentrations in the plants to the sufficiency range. Although with crop residues some P was provided (1.5 kg t−1), the beneficial effects were primarily attributed to increased P acquisition by the millet plants, which was reflected in enhanced root growth in the topsoil (0–10 cm).